Starting aid for fluorescent lamp

ABSTRACT

A starting aid in combination with a fluorescent lamp is provided. The lamp comprises a glass discharge tube ( 2 ) which includes a discharge path and is convoluted to have a plurality of discharge tube legs. These legs extend into and are secured in place in a plastic housing. Lamp electrodes ( 40, 42 ) are located at respective end points of a discharge path and disposed in some of the discharge tube legs. The lamp electrodes are connected to means suitable for electrically connecting to a socket. The starting aid comprises an electrical connector disposed in the plastic housing of the florescent lamp. The starting aid has a first end and a second end. The first end is connected to the means suitable for electrically connecting to the socket. The second end is secured to an end portion of an electrodeless discharge tube leg. At least a part of the electrical connector is formed as a spring. A fluorescent lamp system with a starting aid is also provided. The lamp system comprises a ballast unit which controls electrical power received from an external power source. The electrodes ( 40, 42 ) of a sealed lamp unit are connected electrically to the ballast unit and disposed in adjacent tube legs of the sealed lamp unit. A first electrical connector ( 36 ) is connected with one end to the first lamp electrode ( 40 ). Its other end is secured at least to one of the tube legs located along the discharge path consecutively next to the tube leg in which the second electrode ( 42 ) is disposed. A second electrical connector ( 38 ) with one end is connected to the second lamp electrode ( 42 ). Its other end is secured at least to one of the tube legs located along the discharge path consecutively next to the tube leg in which the first electrode is disposed.

FIELD OF THE INVENTION

This invention relates to a starting aid for fluorescent lamps and, andmore particularly, to a structure and electrical connection of thestarting aid suitable for reducing the starting voltage of the lamp.

BACKGROUND OF THE INVENTION

Fluorescent lamps, especially compact fluorescent lamps of higherwattage, e.g. 26 W or above this wattage, require high starting voltage.This problem arises primarily at amalgam dosed lamps operated at roomtemperature, but also occurs in the event of pure mercury dosed lampsoperated at lower ambient temperature. The high starting voltage causescompatibility issues even in the field of an increasing number ofballasts and applications. The problem is also related to the fact thatan increasing number of luminaries have plastic reflectors rather thanmetallic ones and the plastic reflector cannot serve as a starting aid.It is difficult to meet the starting voltage requirements specified bythe standards without sacrificing lumen output, lumen maintenance andlifetime in the wattage range mentioned.

U.S. Pat. No. 4,523,126 describes a starting aid for shaped dischargelamps. The starting aid is a metal band secured to the discharge tube.The starting voltage reduction sharply depends on the location of thestarting bands. This feature implies an accurate positioning of thestarting bands relative to cathode location. Experiments were conductedin order to prove the effectiveness of the solution described in theabove-cited patent when applied at compact fluorescent lamps, but nosignificant starting voltage reduction could be accomplished. It isbelieved that the negative result is due to the different lamp geometryand the different filling gas. A further disadvantage of the startingaid according to the cited patent is a loss in light output due to theshielding action of the starting band. Calculating with the preferredwidth of starting bands, the lumen loss expected is in the range of 2–4percent. A further drawback is that a conductive part is placed on atouchable portion of the lamp. When the hot cathode hits the wall of theglass tube at the end of the life of the lamp the wall may crack and acurrent path may be formed to the metallic starting band. The user ofthe lamp may be exposed to electrical shock.

A similar design is described in U.S. Pat. No. 4,701,667 in which a ringshape starting aid is applied to fluorescent lamps. This starting aidmay cause dangerous electric shock and decreases the light output.

Thus there is a particular need to provide a starting aid which reducesthe starting voltage of the fluorescent lamp significantly withoutdecreasing the light output of the lamp and ensures safety againstelectric shock at the end of the life of the lamp.

BRIEF DESCRIPTION OF THE INVENTION

As an exemplary embodiment of one aspect of this invention, a startingaid in combination with a fluorescent lamp is provided. The lampcomprises a glass discharge tube which includes a discharge path and isconvoluted to have a plurality of discharge tube legs. These legs extendinto and are secured in place in a plastic housing. Lamp electrodes arelocated at respective end points of a discharge path and disposed insome of the discharge tube legs. The lamp electrodes are connected tomeans suitable for electrically connecting to a socket. The starting aidcomprises an electrical connector disposed in the plastic housing of thefluorescent lamp. The starting aid has a first end and a second end. Thefirst end is connected to the means suitable for electrically connectingto the socket. The second end is secured to an end portion of anelectrodeless discharge tube leg. At least a part of the electricalconnector is formed as a spring.

In an exemplary embodiment of another aspect of the present invention, afluorescent lamp system with a starting aid is provided. The lamp systemcomprises a ballast unit which controls electrical power received froman external power source. A sealed lamp unit contains a gas and includesa plurality of discharge tube legs and a continuous discharge path.First and second lamp electrodes are located at respective end points ofthe discharge path. The electrodes are connected electrically to theballast unit and disposed in adjacent tube legs of the sealed lamp unit.A first electrical connector is connected with one end to the first lampelectrode. Its other end is secured at least to one of the tube legslocated along the discharge path consecutively next to the tube leg inwhich the second electrode is disposed. A second electrical connector isconnected with one end to the second lamp electrode. Its other end issecured at least to one of the tube legs located along the dischargepath consecutively next to the tube leg in which the first electrode isdisposed.

This structure and electrical connection of the starting aid has anumber advantages over the prior art. One advantage is that the startingvoltage of the lamp is reduced significantly due to the structure andelectrical cross connection of the two electrical connectors of thestarting aid. Another advantage is that dangerous electrical shocks areavoided since the starting aid is located in the plastic housing of thelamp and there is no additional metal component part on the surface ofthe lamp that can be touched by the user. A further advantage is thatthe lumen output of the lamp is not decreased by the starting aid sincethe structure according to the present invention is not applied to alight-emitting surface of the lamp.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an electrical connection of a starting aid with twoelectrical connectors schematically;

FIG. 2 shows another possible connection of the starting aid;

FIG. 3 shows a further possible connection of the starting aid;

FIG. 4 is a perspective view in partial axial-section of a shell portionof a lamp housing with starting aid;

FIG. 5 is a top view of the shell portion including the elements of astarting aid with bent wire spring;

FIG. 6 is a side view in axial-section of the shell portion according toFIG. 5;

FIG. 7 is a perspective view partly in axial-section of the shellportion according to FIG. 5;

FIG. 8 is an axial-section view of the shell portion with a dischargetube of a compact fluorescent lamp and a plastic support plate mountedwith leaf springs;

FIG. 9 is a top view of the compact fluorescent lamp according to FIG.8;

FIG. 10 is a perspective view in partial axial-section of the lampaccording to FIG. 8;

FIG. 11 is a side view of the plastic support plate including theelements of a starting aid with the leaf spring;

FIG. 12 is a top view of the plastic support plate according to FIG. 11;

FIG. 13 is a perspective view of the plastic support plate with the leafsprings.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1–3 illustrate the electrical connection of the starting aid. Eachof the figures is a bottom view of a compact fluorescent lamp, showingthe layout of the discharge tube. The discharge tube includes of U-shapesections having tube legs, which are connected to each other by bridgesestablishing a continuous discharge path. The discharge path starts fromthe tube end with a first electrode 40, goes through electrodeless tubelegs 54, 56, 58, 48, 46, 44 and terminates at a tube leg with a secondelectrode 42. The ends of some electrodeless tube legs 44, 46, 54, 56are metallized, the metallized tube ends are indicated by hatching inthe figures. First and second electrical connectors 36, 38 arecross-connected, i.e. the first electrode 40 is coupled with at leastone of the ends of the electrodeless discharge tube legs located alongthe discharge path consecutively next to the tube leg in which thesecond electrode 42 is disposed. The second electrode 42 is in turncoupled with at least one of the ends of the electrodeless dischargetube legs located along the discharge path consecutively next to thetube leg in which the first electrode 40 is disposed. Due to thiscross-connection, a capacitive current comes into being and makes thelamp start at a reduced voltage applied to the electrodes.

Referring now to FIG. 1, the first and second electrodes 40, 42 arelocated at respective end points of the discharge path. The firstelectrical connector 36 is connected with one end to the first lampelectrode 40 and its other end is secured to the second tube leg 46located along the discharge path next to the tube leg in which thesecond electrode 42 is disposed. The second electrical connector 38 isconnected with one end to the second lamp electrode 42 and its other endis secured to the second tube legs 56 located along the discharge pathnext to the tube leg in which the first lamp electrode 40 is disposed.

As FIG. 2 shows, while one end of the electrical connectors 36, 38 isconnected to the electrodes similarly to the connection in FIG. 1, theother end of the first electrical connector 36 is secured to the firstelectrodeless tube leg 44 located next to the tube leg in which thesecond electrode 42 is disposed. The other end of the second electricalconnector 38 is secured to the first electrodeless tube leg 54 next tothe tube leg in which the first electrode 40 is disposed.

As FIG. 3 illustrates, while one end of the electrical connectors 36, 38is connected to the electrodes 40, 42 similarly to the connection ofFIGS. 1 and 2, the other end of the first electrical connector 36 issecured to two consecutive electrodeless tube legs 44, 46 located nextto the tube leg in which the second electrode 42 is disposed. The otherend of the second electrical connector 38 is secured to two consecutiveelectrodeless tube legs 54, 56 located next to the tube leg in which thefirst electrode 40 is disposed.

FIGS. 4–13 illustrate structural embodiments of the starting aid.Referring now to FIG. 4, it shows a shell portion 20 which is one partof the to plastic housing of a compact fluorescent lamp. The other partof the housing is a cap portion which will be described in theforthcoming figures. Additionally, a socket (not shown) belongs to thelamp system generally including a ballast unit in the event of compactfluorescent lamps of plug-in type. The mechanical attach to the socketis established by a support plug 30 protruding from the bottom of theshell portion 20, while four contact pins 8 are provided for electricalconnection towards the ballast unit. In the figure, an electricalconnector of the starting aid is represented by a contact wire 24 madeof chrome-steel material. Its first end is attached to a contact pin 8,and its second end is formed as a helical spring 10 embedded in a nest12 of a protrusion 14 extending from the bottom wall of the shellportion 20. A middle part of the contact wire 24 is led through plasticguides 26 from the contact pin 8 up to the protrusion 14. Only onecontact wire 24 is shown in the figure, however a second one can also bedisposed within the shell portion 20. During the assembly of the lamp,the first end of the contact wire 24 together with a lead-in wire of anelectrode will be crimped in a contact pin 8 connecting the electricalconnector of the starting aid to the electrode of the lamp. The free endof the helical spring 10 will resiliently lean against one of themetallized electrodeless tube ends thereby pressing the second end ofthe contact wire 24 to an end portion of the electrodeless dischargetube. An effective capacitive coupling comes into being between theelectrical connector of the starting aid and the discharge path point atthe electrodeless tube end. Due to the effective capacitive coupling, anadditional electrical potential is formed along the discharge pathbetween the electrodes which modifies the breakdown path of theelectrical field and reduces the starting voltage.

In FIGS. 5–7, another embodiment of the starting aid is shown. The firstend of the electrical connector is connected to the contact pin 8 andthe second end is simply bent to form a wire spring 28. The middleportion is a contact wire 24 and is led through plastic guides 26similarly to the previous embodiment. The wire spring 28 is nested in aplastic deflector 34 protruding from the bottom of the shell portion 20.During the lamp-making process, when the cap portion 22 is fixed to theshell portion 20, the free end of the wire spring 28 will resilientlylean against one of the metallized electrodeless tube ends, while thefirst end of the contact wire 24 together with a lead-in wire of anelectrode will be crimped in a contact pin 8 similarly to the embodimentaccording to FIG. 4. The metallization of the tube ends can be made by adabber print process or by sprinkling a paint containing a metal in afew microns of thickness. In FIG. 5, two contact wires 24 with wiresprings 28 are shown secured in place in the shell portion 20.

Another embodiment of the starting aid is shown in FIGS. 8–10. Thedischarge tube 2 is fixed in the cap portion 22 by the ends of the tubelegs. The first and second electrode 40, 42 are inserted into twoadjacent tube legs, the others are electrodeless tube legs 44, 46, 48,54, 56, 58. The end portions of two electrodeless tube legs 46, 56 aremetallized. A plastic support plate 18 including two leaf sprigs 16 isattached to the cap portion 22. The free ends of the leaf springs 16lean resiliently against the ends of the metallized electrodelessdischarge tube legs 46, 56 establishing an electrical connection withthem. The other end thereof is pressed into the plastic support plate 18and welded to a conductive wire which is connected to the electrodes andthe contact pin of the shell portion illustrated in FIG. 4 during thelamp assembly process.

FIGS. 11–13 show a detailed structure of the plastic support plate 18with the leaf spring 16. The plastic support plate 18 is secured in thecap portion of the lamp by ribs 32 protruding substantially parallel toa longitudinal axis of the lamp at an edge portion of the plasticsupport plate. The leaf springs 16 are inserted into the plastic supportplate 18 by snapping one of their ends into the plastic support plate18. The leaf springs 16 are made of resilient steel and serve as thesecond ends of the electrical connectors, the first ends of whichcorrespond to the first ends of the conductive wires mentioned above.Insulators 6 protrude from the side of the plastic support plate 18opposite to the tube ends in order to promote the insulation of theconducting elements mounted in the housing of the lamp.

In further embodiments, the spring portion of the electrical connectorcan be made of conductive sponge or rubber.

Experiments were conducted in order to prove the effectiveness of thestarting aid according to the embodiments of the invention. The startingaids were built in the plastic housing of compact fluorescent lamps oftypes 42 W HEX and 42 W OCT. The starting voltages at different ambienttemperatures were investigated. The results of the test are shown inTable 1.

TABLE 1 Starting voltage [Vms] 42W HEX 42W OCT without with aid, no withaid, without Temp aid metallization metallization aid with aid 25° C.523 515 359 633 530 10° C. 536 n/a 396 647 524 −15° C. 584 n/a 454 660575

Another test was made for different types of starting aids, the resultof which is shown in Table 2.

TABLE 2 It is Starting seen voltage Type of starting aid in [Vms]Starting aid connected to the tube end second from the FIG. 1 555electrodes, cross connection Starting aid connected to the tube endfirst from the FIG. 2 513 electrodes, cross connection Starting aidconnected to the tube ends first and second FIG. 3 533 from theelectrodes, cross connection

As it is seen in the table, the most significant reduction can beaccomplished by the starting aid described with reference to FIG. 2.

The starting aid structure and the electrical cross-connection of itstwo electrical conductors reduces the starting voltage of thefluorescent lamp significantly without decreasing the light output ofthe lamp and ensure safety against electric shock at the end of the lifeof the lamp. The two electrical conductors of the starting aid provideadditional two discharge path points between the electrodes of the lamp.The voltage potential applied to the lamp electrodes is also applied tothese additional discharge path points thereby modifying the breakdownpath of the electrical field significantly. The springy structure of theelectrical conductors of the starting aid ensures a firm capacitivecoupling towards the discharge path thereby increasing the effectivenessof the additional discharge path points. An even more effective couplingis accomplished by the metallized end portion of the tube legs to whichthe electrical conductors are secured. Since the starting aid of thepresent invention is disposed in the plastic housing, it cannot causedangerous electric shock and does not decrease the lumen output of thelamp.

One skilled in the art may propose or make modification to the structureand/or function and/or manner of the disclosed embodiments withoutdeparting from the scope and extent of the invention.

1. A fluorescent lamp comprising: a glass discharge tube having adischarge path and a plurality of discharge tube legs extending into andsecured in place in a housing; lamp electrodes located at respective endpoints of a discharge path and disposed in some of the discharge tubelegs, the lamp electrodes being connected to means for electricallyconnecting to a socket; a starting aid comprising: an electricalconnector disposed in the housing and having a first end and a secondend; the first end being connected to the means for electricallyconnecting to the socket, and the second end being secured to an endportion of an electrodeless discharge tube leg; and at least a part ofthe second end of the electrical connector being formed as a spring. 2.The lamp of claim 1 in which the end portion of the electrodelessdischarge tube leg to which the second end of the electrical connectoris secured is metallized.
 3. The lamp of claim 1 in which the means forelectrically connecting to a socket is a contact pin.
 4. The lamp ofclaim 1 in which the electrical connector is a wire coiled to form ahelical spring at the second end thereof for pressing the second end tothe end portion of the electrodeless discharge tube leg.
 5. The lamp ofclaim 4 in which the helical spring is located in a nest formed in aprotrusion of the housing.
 6. The lamp of claim 3 in which the first endof the electrical connector is crimped to the contact pin.
 7. The lampof claim 1 in which the electrical connector is a wire connected to aleaf spring forming the second end of the electrical connector forpressing the second end to the end portion of the electrodelessdischarge tube leg.
 8. The lamp of claim 7 in which one end of the leafspring is fixed to a support plate being disposed in the housing.
 9. Thelamp of claim 1 in which the housing comprises a shell portion and a capportion fixed to each other, and the discharge tube legs are secured tothe cap portion and the means for electrically connecting to a socket isfixed in the shell portion.
 10. A fluorescent lamp system having astarting aid, the fluorescent lamp system comprising: a ballast unitcontrolling electrical power received from an external power source; asealed lamp unit containing a gas and having a plurality of dischargetube legs and a continuous discharge path; first and second lampelectrodes located at respective end points of the discharge path, theelectrodes being connected electrically to the ballast unit and disposedin adjacent tube legs of the sealed lamp unit; a first electricalconnector having an end connected to the first lamp electrode andanother end secured at least to one of the electrodeless tube legslocated along the discharge path consecutively next to the tube leg inwhich the second electrode is disposed; and a second electricalconnector having an end connected to the second lamp electrode andanother end secured at least to one of the electrodeless tube legslocated along the discharge path consecutively next to the tube leg inwhich the first electrode is disposed; and the other end of the firstelectrical connector is secured at least to one of the electrodelesstube legs located along approximately one-half of the discharge pathconsecutively next to the tube leg in which the second electrode isdisposed; and the other end of the second electrical connector issecured at least to one of the electrodeless tube legs located alongapproximately one-half of the discharge path consecutively next to thetube leg in which the first electrode is disposed.
 11. The system ofclaim 10 in which the other end of the first electrical connector issecured to the first electrodeless tube leg located along approximatelyone-half of the discharge path next to the tube leg in which the secondelectrode is disposed; and the other end of the second electricalconnector is secured to the first electrodeless tube leg located alongapproximately one-half of the discharge path next to the tube leg inwhich the first electrode is disposed.
 12. The lamp of claim 1 whereinthe housing is made of plastic.
 13. The lamp of claim 8 wherein thesupport plate is made of plastic.
 14. A starting aid for a fluorescentlamp comprising: an electrical connector having a first end and a secondend, the connector being disposed in a plastic housing of the lamp; thefirst end connected to a means for electrically connecting the lamp; thesecond end being connected to an end portion of an electrodelessdischarge tube leg of the lamp; and at least part of the connector isformed as a resilient member.
 15. The starting aid of claim 1 whereinthe end portion is metallized.
 16. The starting aid of claim 1 whereinthe means for electrically connecting is a contact pin.
 17. The startingaid of claim 1 wherein the electrical connector is a spring fixed at thesecond end.
 18. The starting aid of claim 1 wherein the resilient memberis a helical spring.
 19. The starting aid of claim 18 wherein thehelical spring is located in a protrusion of the housing.
 20. Thestarting aid of claim 16 wherein the first end of the connector iscrimped to the contact pin.
 21. The starting aid of claim 13 wherein theelectrical connector is a wire connected to a leaf spring forming thesecond end of the connector.
 22. The starting aid of claim 20 whereinone end of the leaf spring is fixed to a plastic support plate disposedin the housing.
 23. The starting aid of claim 13 wherein the housingcomprises: a shell portion; a cap portion fixed to the shell portion;the discharge tube leg is secured to the cap portion; and the means forelectrically connecting is fixed in the shelf portion.